Problem: Solve for $k$ : $-23 + k = 13$
Answer: Add $23$ to both sides: $ \begin{eqnarray} \\ -23 + k &=& 13 \\ \\ {+23} && {+23} \end{eqnarray} $ $ \begin{eqnarray} \hphantom{-23 + k} &\hphantom{=}& \hphantom{13} \\ k &=& 13 {+ 23} \\ \end{eqnarray} $ Simplify. $ k = 36$